1. Field of the Invention
The present invention relates to a dielectric ceramic, and a laminated ceramic capacitor configured with the use of the dielectric ceramic.
2. Description of the Related Art
Laminated ceramic capacitors, a major applications of the present invention, are commonly manufactured as follows.
First, a ceramic green sheet containing a dielectric ceramic raw material is prepared whose surface is provided with a conductive material to serve as internal electrodes with a predetermined pattern.
Next, a plurality of ceramic green sheets including ceramic green sheets provided with the conductive material are laminated and subjected to thermocompression bonding, thereby manufacturing an integrated raw (green) laminated body.
Next, this raw laminated body is calcined, thereby obtaining a calcined laminated body. Internal electrodes composed of the conductive material described above are formed in this laminated body.
Then, external electrodes are formed on the outer surfaces of the laminated body so as to be electrically connected to specific one of the internal electrodes. The external electrodes are formed, for example, by providing a conductive paste containing conductive metal powder and glass frit onto the outer surfaces of the laminated body and baking the conductive paste. In this way, a laminated ceramic capacitor is completed.
It is desirable in the laminated ceramic capacitors to use inexpensive Ni for the internal electrodes, in order to reduce the manufacturing cost. Since Ni is a base metal, the atmosphere for calcination needs to be brought into a reducing atmosphere condition in order to prevent Ni from being oxidized during the calcination of the laminated body.
In order to carry out the calcination in a reducing atmosphere, the dielectric ceramic material is required to have resistance to reduction. As a material which exhibits a certain level of insulation properties even after calcination under a reducing atmosphere, Japanese Patent Application Laid-Open No. 2002-80278 (Patent Document 1) discloses ceramic compositions of the (Sr, Ca)(Ti, Zr)O3 type.